1. Field of the Invention
The present invention relates to an ink, an ink-jet recording process, and an instrument making use of the ink. More particularly it relates to an ink, an ink-jet recording process, a recording unit, an ink-jet recording apparatus and an ink cartridge that are capable of achieving highly detailed and high-image quality recording not only on coated paper specially prepared for ink-jet recording but also on non-coated paper such as paper for copying, paper for reporting, notepaper, letter paper, bond paper or continuous slip paper, i.e., what is called a plain paper, commonly used in offices and homes.
2. Related Background Art
Inks with greatly various manners of being composed have been hitherto reported in respect of inks for an ink-jet recording. In particular, in recent years, detailed research and developments have been made from various approaches such as composition and physical properties of inks so that a good record can be made even on a plain paper such as paper for copying, paper for reporting, notepaper, letter paper, bond paper or continuous slip paper, commonly used in offices.
For example, inks usually contain high-boiling organic solvents such as glycols for the purposes of anti-drying, anti-clogging and so forth. When recording is carried out using such inks on a plain paper having a high degree of sizing, ink does not readily penetrate into paper an the part on which a record has been made does not dry well, so that when recorded characters or the like are touched, the hand may be stained with ink, or the characters are rubbed to become smeared. Thus, there has been a problem on fixing performance.
Under such circumstances, in order to increase the penetrability of ink into paper, Japanese Patent Application Laid-open No. 55-29546 proposes a method in which a surface active agent is added in ink in a large quantity. In such an instance, however, the following troubles have been caused: Feathering occurs very frequently on some kind of paper; when filled in an ink-jet recording head, the ink recedes from the orifice surface depending on the structural conditions of the head, resulting in no ejection of ink, or on the other hand the whole of the orifice surface becomes wet, also resulting in no ejection of ink.
Japanese Patent Application Laid-open No. 56-57862 also proposes a method in which the pH of ink is set to the alkaline side. In this instance, however, there are the disadvantages such that the ink is harmful when touched with hands or that no good results can be obtained in view of both feathering and drying performance when the ink is used on a paper containing a certain kind of sizing agent, e.g., a neutralized paper.
Besides the foregoing, various improvements have been attempted. Up to the present, however, no ink is known which can well settle all the above problems on feathering, drying performance and safety of ink, and also the problem of clogging.